Jason LaVeris/FilmMagic(NEW YORK) -- After a third season in which the popular PBS series Downton Abbey lost two of its main characters, PBS is announcing the return of a familiar face and the addition of several new ones.

Shirley MacLaine, who appeared earlier this season as Martha Levinson, the outspoken mother of Cora, Countess of Grantham (Elizabeth McGovern), will return for season 4.

New additions to the cast include Tom Cullen, whose Lord Gillingam is described as “an old family friend of the Crawleys,” and Harriet Walter, who takes on the part of Lady Shackleton, “an old friend of the Dowager.”

Season 4 of the British class drama will also introduce aristocrat Charles Blake, played by Julian Ovenden. New Zealand-born opera star Kiri Te Kanawa — a real-life dame — will also appear as a guest of the Crawley family.

This past season, the show saw the shocking departures of Dan Stevens, who played Matthew Crawley, and Jessica Brown Findlay, who portrayed Lady Sybil.

Now it appears another familiar face may be leaving. Actress Siobhan Finneran, who plays housemaid Mrs. O’Brien, the character fans love to hate, will not be returning for the new season.

Finneran told the U.K.’s Daily Mirror last week, “I’m not doing any more, O’Brien is a thoroughly despicable human being — that was great to play.”

The fourth season will premiere in the U.K. next fall and in the U.S. the following winter.